1. Field
The present disclosure relates to a fuel cell stack.
2. Description of the Related Art
In general, a solid polymer electrolyte fuel cell includes a solid polymer electrolyte membrane, which is a polymer ion-exchange membrane. The fuel cell includes a membrane electrode assembly (MEA), in which an anode electrode is disposed on one surface of the solid polymer electrolyte membrane and a cathode electrode is disposed on the other surface of the solid polymer electrolyte membrane. The anode electrode and the cathode electrode each include a catalyst layer (electrode catalyst layer) and a gas diffusion layer (porous carbon).
The membrane electrode assembly and separators (bipolar plates) that sandwich the membrane electrode assembly constitute a power generation cell (unit fuel cell). A predetermined number of power generation cells are stacked and used, for example, as a vehicle fuel cell stack.
In the fuel cell stack, the temperatures of some of the power generation cells tend to decrease more easily than those of other power generation cells due to dissipation of heat to the outside. For example, the temperature of a power generation cell that is disposed at an end in the stacking direction (hereinafter, referred to as an “end power generation cell”) decreases particularly easily, because heat of the end power generation cell is dissipated to the outside through a terminal plate, an end plate, and the like, which are adjacent to the end power generation cell.
For example, Japanese Unexamined Patent Application Publication No. 2001-68141 describes a fuel cell stack for solving this problem. Referring to FIG. 6, the fuel cell includes a stacked body 2 in which a plurality of cell units 1 are stacked. A pair of collector plates 3a and 3b are disposed at both ends of the stacked body 2 in the stacking direction. A pair of insulation plates 4a and 4b, for electrical insulation, are respectively disposed outside of the collector plates 3a and 3b. 
Manifold plates 5a and 5b are respectively disposed outside of the insulation plates 4a and 4b. The manifold plates 5a and 5b apply a fastening force to the entirety of the fuel cell.
Each of the cell units 1 has a cooling water channel 6, extending in a direction along an electrode surface. An inlet and an outlet of the cooling water channel 6 are respectively connected to a cooling water supply manifold 7a and a water-guide manifold 7b. 
The manifold plate 5a has a cooling water inlet 8a and a cooling water outlet 8b. The cooling water inlet 8a is connected to the cooling water supply manifold 7a, which extends in the stacking direction. The cooling water outlet 8b is connected to the water-guide manifold 7b via a cooling water channel 9, which is formed in the manifold plate 5b so as to make a vertical U-turn.